Friend of mine had one on his, wait for it, perineum! Yes, that lovely little bit of real estate between your ball bag and your a-hole. He had to have it, ahem, lanced by a doctor. It was caused by an ingrown hair follicle brought about by a lot of bike riding.

I'm not sure what must have been worse; the pain of having it lanced or the ignominy of the position he must have had to adopt to allow the doctor access in the first place.